1. Field of the Invention
The invention relates to a test system and method. More particularly, the invention relates to a test system and method used for testing a capacitive touch sensor.
2. Description of Related Art
FIG. 1 is diagram illustrating a conventional test system of a capacitive touch sensor, wherein the test system 110 is used for testing the capacitive touch sensor 130, and the test system 110 includes a micro controller 111 and a variable capacitor VC1. The variable capacitor VC1 is electrically connected to a sensing port P11 of the capacitive touch sensor 130 to serve as a capacitor to be tested. Moreover, the micro controller 111 is electrically connected to an output port P12 of the capacitive touch sensor 130 for receiving test information D11.
During a test process, the micro controller 111 adjusts a capacitance of the variable capacitor VC1. On the other hand, the capacitive touch sensor 130 controls conductive states of switches SW11 and SW12 through switching signals phA and phB, so as to charge or discharge the variable capacitor VC1. Moreover, an integrating circuit formed by a capacitor C1 and an operational amplifier 131 may convert a current provided by the variable capacitor VC1 into a corresponding integrating voltage VG. Moreover, an analog-to-digital converter (ADC) 132 converts the integrating voltage VG into the corresponding test information D11. In this way, the micro controller 111 in the test system 110 can read the test information D11 to determine whether an operation of the capacitive touch sensor 130 is normal.
However, the capacitive touch sensor 130 is mainly used to detect a tiny capacitance variation, so that the test system 110 must have a precise variable capacitor VC1 for effectively testing the capacitive touch sensor 130. For example, if a resolution of the ADC 132 is 10 bits, and the capacitive touch sensor 130 is used to detect a capacitor with a capacitance range from 4 f to 4.096 p farads, now the test system 110 must have the variable capacitor VC1 with a variable capacitance range from 4 f to 4.096 p farads, and the variable capacitance VC1 must have a feature of fine-tunable for every 4 f farads. However, process variations are usually occurred during a semiconductor fabrication process, so that it is hard to fabricate such precise variable capacitor VC1.